Combustion air chargers, such as turbochargers or superchargers, have been employed with engines, particularly internal combustion engines, for many years. In a turbocharger, at least one rotary compressor wheel is driven by the exhaust of the engine. In the case of a supercharger, at least one rotary compressor wheel is driven mechanically, usually by the rotary output of the engine. In either case, a compressor wheel is employed to compress ambient air prior to its admission to the engine to support combustion therein. Because the air is compressed, a given volume thereof will have a greater mole content of oxygen than an otherwise equal of volume of air at ambient pressure. As a consequence, the additional oxygen permits the combustion of a greater quantity of fuel so that for a power plant of a given size, a greater power output may be derived as a result of the charging of the combustion air.
Over the years, it has been determined that the efficiency of such combustion air charging devices can be improved through the use of a so-called intercooling system. Because the air is heated as it is compressed, part of the efficiency derived by employing the combustion air charging device in the first place, i.e., the densification of the combustion air charged to the engine, is lost because a volume of hot compressed air will contain less oxygen than an equal volume of cooler compressed air when both are at the same pressure. Thus, for a given pressure, upon admission to an engine for combustion, a cooler combustion air charge will allow the development of more power within the engine than the same charge at the same pressure if at a higher temperature.
Consequently, intercoolers as mentioned previously have been employed to cool the air after it exits the combustion air charger (or a stage thereof) and prior to its admission to the engine so as to provide, for any given pressure, a maximum mole content of oxygen.
In many cases, the intercooler will be employed as a conventional, rectangular-shaped heat exchanger and is mounted side-by-side or to the front or rear of the usual heat exchanger employed for cooling engine coolant. While this sort of an arrangement adequately handles the cooling of the pressurized combustion air, it may have certain constraints in terms of size and the volume available in an engine compartment as, for example, in a vehicle, that houses both the engine and the various heat exchangers employed for cooling. It also may require extensive hose connections between the turbocharger, the intercooler and the engine combustion air inlet which necessarily require relatively large diameter hoses because of the low density of the combustion air and the consequent large volume thereof.
It has therefore been proposed to incorporate the intercooler within the combustion air charger itself to provide a more compact combustion air charging and intercooling system as well as to avoid large, bulky hose connections to the extent possible. The goal here is to incorporate the intercooling heat exchanger within the combustion air charger in such a way that it may be easily serviced, requires a minimum of plumbing connections and does not unduly increase the bulk of the combustion air charger.
Furthermore, an internally mounted intercooler is more conveniently provided with a liquid cooling heat exchange fluid, such as engine coolant, which may be at relatively high pressure. Therefore, the intercooler must be capable of withstanding such high pressures. At the same time, thermal cycling and pressure cycling can also contribute to fatigue of the heat exchanger. Thus, the heat exchanger must be fabricated to withstand high pressure and be resistant to fatigue caused by thermal and pressure cycling.
The present invention is directed toward the provision of advantageous solutions to these problems in an intercooling heat exchanger that is intended to be located internally within a rotary radial discharge compressor that may have a variety of uses as in a combustion air charger for an engine, as well as toward the provision of a pressure resistant heat exchanger generally.